From: Peter Zijlstra <peterz@infradead.org>
To: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Linux PM <linux-pm@vger.kernel.org>,
Daniel Lezcano <daniel.lezcano@linaro.org>,
Doug Smythies <dsmythies@telus.net>,
LKML <linux-kernel@vger.kernel.org>,
Giovanni Gherdovich <ggherdovich@suse.cz>,
"Rafael J. Wysocki" <rjw@rjwysocki.net>
Subject: Re: [PATCH v2] cpuidle: Use nanoseconds as the unit of time
Date: Fri, 8 Nov 2019 10:39:19 +0100 [thread overview]
Message-ID: <20191108093919.GJ4114@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <CAJZ5v0jM3+qMvO6dx=FmK-xF0q3YKOwBf-yUPXSBfRjxJ59Cpg@mail.gmail.com>
On Fri, Nov 08, 2019 at 02:44:13AM +0100, Rafael J. Wysocki wrote:
> On Thu, Nov 7, 2019 at 3:25 PM Rafael J. Wysocki <rjw@rjwysocki.net> wrote:
> >
> > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> >
> > Currently, the cpuidle subsystem uses microseconds as the unit of
> > time which (among other things) causes the idle loop to incur some
> > integer division overhead for no clear benefit.
> >
> > In order to allow cpuidle to measure time in nanoseconds, add two
> > additional fields, exit_latency_ns and target_residency_ns, to
> > represent the exit latency and target residency of an idle state
> > in nanoseconds, respectively, to struct cpuidle_state_usage and
> > initialize them with the help of the corresponding values in
> > microseconds provided by drivers. In addition to that, change
> > cpuidle_governor_latency_req() to return the idle state exit
> > latency constraint in nanoseconds.
> >
> > With that, meeasure idle state residency (last_residency_ns in
> > struct cpuidle_device and time_ns in struct cpuidle_driver) in
> > nanoseconds and update the cpuidle core and governors accordingly.
> >
> > However, the menu governor still computes typical intervals in
> > microseconds to avoid integer overflows.
>
> Since this addresses all of the comments received by the RFC version
> that was posted over a month ago and I don't see any more issues with
> it, I'm tempted to simply queue it up for 5.5 unless somebody sees a
> good enough reason why that would be a bad idea.
Nah, have at.
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
prev parent reply other threads:[~2019-11-08 9:39 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-06 10:30 [PATCH] cpuidle: Use nanoseconds as the unit of time Rafael J. Wysocki
2019-11-07 14:25 ` [PATCH v2] " Rafael J. Wysocki
2019-11-08 1:44 ` Rafael J. Wysocki
2019-11-08 8:45 ` Doug Smythies
2019-11-08 9:45 ` Rafael J. Wysocki
2019-11-08 17:04 ` Doug Smythies
2019-11-10 16:48 ` Rafael J. Wysocki
2019-11-10 17:24 ` Rafael J. Wysocki
2019-11-10 18:09 ` Doug Smythies
2019-11-10 22:12 ` Doug Smythies
2019-11-11 21:29 ` Rafael J. Wysocki
2019-11-08 9:39 ` Peter Zijlstra [this message]
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